On serial lines, a ``de facto'' standard known as SLIP or Serial Line IP is frequently used. A modification of SLIP is known as CSLIP, or compressed SLIP, and performs compression of IP headers to make better use of the relatively low bandwidth provided by serial links. A different serial protocol is PPP, or Point-to-Point Protocol. PPP has many more features than SLIP, including a link negotiation phase. Its main advantage over SLIP is, however, that it isn't limited to transporting IP datagrams, but that it was designed to allow for any type of datagrams to be transmitted.